 <html>
     <head>
     <title>区块实验</title>
     </head>
     <body>
        <table border="1" width="300">
            <tr align="center">
              <td><select size="1"> 
                <option>1</option>
                <option selected>2</option>
                <option selected>3 </option>
                <option selected>4</option>
              </select>
             </td>
             <td><select size="1"> 
                <option>1</option>
                <option selected>2</option>
                <option selected>3 </option>
                <option selected>4</option>
              </select>
             </td>
             <td><select size="1"> 
                <option>1</option>
                <option selected>2</option>
                <option selected>3 </option>
                <option selected>4</option>
              </select>
             </td>
             <td><select size="1"> 
                <option>1</option>
                <option selected>2</option>
                <option selected>3 </option>
                <option selected>4</option>
              </select>
             </td>
            </tr>
            <tr align="right">
                <td><select size="1"> 
                    <option>1</option>
                    <option selected>2</option>
                    <option selected>3 </option>
                    <option selected>4</option>
                  </select>
                 </td>
                 <td><select size="1"> 
                    <option>1</option>
                    <option selected>2</option>
                    <option selected>3 </option>
                    <option selected>4</option>
                  </select>
                 </td>
                 <td><select size="1"> 
                    <option>1</option>
                    <option selected>2</option>
                    <option selected>3 </option>
                    <option selected>4</option>
                  </select>
                 </td>
                 <td><select size="1"> 
                    <option>1</option>
                    <option selected>2</option>
                    <option selected>3 </option>
                    <option selected>4</option>
                  </select>
                 </td>
            </tr>
            <tr>
                <td><select size="1"> 
                    <option>1</option>
                    <option selected>2</option>
                    <option selected>3 </option>
                    <option selected>4</option>
                  </select>
                 </td>
                 <td><select size="1"> 
                    <option>1</option>
                    <option selected>2</option>
                    <option selected>3 </option>
                    <option selected>4</option>
                  </select>
                 </td>
                 <td><select size="1"> 
                    <option>1</option>
                    <option selected>2</option>
                    <option selected>3 </option>
                    <option selected>4</option>
                  </select>
                 </td>
                 <td><select size="1"> 
                    <option>1</option>
                    <option selected>2</option>
                    <option selected>3 </option>
                    <option selected>4</option>
                  </select>
                 </td>
            </tr>
        </table>
     </body>
 </html>